1. Technical Field
The present invention relates to external power supply for consumer electronics, and more particularly, to a power-supplying device adaptive to connect a portable electronic device and act as a backup power source that provides a variable power capacity.
2. Description of Related Art
Currently, a rechargeable battery is a common power source for various portable consumer electronics, such as mobile phones, laptops, digital cameras, music players, etc.
For charging such a rechargeable battery, a specific charger is required to adjust the AC power from the power grid into a certain potential. Where the power grid is inaccessible, charging is impossible and the portable device using the battery cannot serve when the battery is exhausted.
To avoid this plight, a portable power supply, or a “power pack”, has been developed. By using the same, users can charge their consumer electronics everywhere despite the accessibility of the power grid.
The existing portable power supply is mainly composed of a rechargeable battery and a control circuit that are packed in an enclosure. The commercialized products are provided with different battery capacities. While a portable power supply having a small capacity is usually compact and light, it cannot serve long. On the other hand, a portable power supply having a small capacity serves long yet is bulky and less portable. In addition, the existing rechargeable battery has its life subject to its age and/or frequency of use and once the battery become poor in performance or broken, the whole power supply is unusable.